[wordup] Squirrel vs. Rattlesnake

[Adam Shand]

Via: Hardcopy of the Dominion Post
Source: http://www.newscientist.com/article/dn12477-squirrels-wield-a- 
hot-secret-weapon.html

Squirrels wield a hot, secret weapon

It's Californian ground squirrel versus rattlesnake in a potentially  
lethal showdown. But the squirrel has a secret weapon that until now  
has remained invisible to the human eye.

The ground squirrel heats up its tail then waves it in the snake's  
face - a form of harassment that confuses the rattler, which has an  
infrared sensing organ for detecting small mammals.

This defensive tactic remained invisible to biologists until they  
looked at the animals through an infrared video camera. Now they  
believe that many other animals might be using infrared weaponry to  
ward off potential predators.

Young California ground squirrels (Spermophilus beecheyi) are easy  
prey for snakes, so protective adults harass the predators while  
puffing up their tails and wagging them.
Infrared organ

Graduate student Aaron Rundus and his supervisor Donald Owings of the  
University of California, Davis, wondered how this might affect the  
snakes’ interaction with the adult squirrels. So he borrowed a  
$35,000 infrared camera from another scientist and spied on squirrel- 
snake stand-offs.

He saw the adults’ tails heat up, presumably due to increased blood  
flow, when they were warning rattlers away – making the squirrel  
appear larger to the snake’s infrared organ.

Confronted with a gopher snake, which has no infrared sensory organ,  
the squirrels wagged their tails but didn’t bother to warm them up  
first.

Tests with robotic squirrels confirmed that a warmed squirrel tail  
made rattlesnakes more likely to act defensively, say Rundus and Owings.

The squirrels themselves do not see in infrared, so they cannot see  
another squirrel's tail heating up. But the snakes can, proving that  
the squirrels have evolved a specific way to deter rattlesnakes.

“It taught us to focus on the perceptual world of the animal we’re  
studying” rather than thinking only of human perceptions, says Rundus.

Journal reference: Proceedings of the National Academy of Sciences  
(DOI: 10.1073/pnas.0702599104)

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